In order to investigate the causal structure of spherically symmetric quantum black holes
with electric charge, in this work we apply the approach of Ref. [1]}
to the Reissner-Nordström metric
\(\mbox{${\rm d}$}s^2=-\left(1+2\,V_{\rm RN}\right)\mbox{${\rm d}$}t^2+\frac{\mbox{${\rm d}$}r^2}{1+2\,V_{\rm RN}}+r^2\,\mbox{${\rm d}$}\Omega ^2\ ,\) 
